My new-to-me 2011 Acura TL is exhibiting intermittent hesitation upon acceleration and there is no check engine light. Maybe I have bad luck because it seems like three of my past four vehicles have done this and I never determined the cause. It seems to occur between 1,500 and 3,000 RPM but once the RPMs get above 3k it accelerates like a bat out of hell. I suspect maybe it's one or more of the coil packs because the previous owner had three of the six replaced shortly before selling it, but if that were the case I would think it would get worse at higher RPM, not better. I've seen these bluetooth and USB diagnostic dongles that plug into the OBDII port and supposedly monitor all of the vehicle functions in real time using a smart phone app or laptop. I'm wondering if this type of tool will allow me to pinpoint what is happening. I've seen several for under $50. Anyone use one of these and successfully diagnosed an engine related issue? https://www.amazon.com/gp/product/B0...=ATVPDKIKX0DER

 

if its not throwing a check engine light, the obdII readers wont do jack chit..

the obdII readers are the same readers they have at autozone...so if you dont live in cali, you can get the car checked for free....instead of spending >$50...

 

you're going to have to trouble shoot.....physically.

why were the coils replaced?
leave engine on and unplug each coil one at a time....engine note should change... if engine note does not change, you have successfully troubleshooted...

 

a misfire will be noticed at idle and lower RPMs and will smooth out at high rpms

 

I have an OBDII reader, but this other product is supposedly for recording parameters in real time so you can monitor them while driving. The coils were replaced because the engine was misfiring badly. I'll measure the primary and secondary coil resistance and see what it is. I've heard some coils don't exhibit problems until the engine warms up, so I suppose I should test them when they're hot. Or take each one out and hit them with a blow dryer while monitoring the resistance

 

Why exactly is that? More momentum at higher RPM and thus less noticeable effect?

 

i forgot if yours is a six speed manual, but if it is....previous owner could have "over-revved" the engine...

 

I believe its because the heads/valves are damaged. at low rpm, it will be more noticable because the cylinder heads are leaking! at high rpm, when the valves are open, it doesnt matter

you need a cylinder compression test and a leak down test

 

No, it's a 5-speed automatic (3.7L SH-AWD). The shop apparently told him it was caused from bad gas. I believe they replaced all of the spark plugs and two or three coils. Coils failing from bad gas is obviously bogus, so it makes me wonder if the others are on their way out as well.

 

Oh man, I hope that isn't the reason. It doesn't do it all the time though, and it idles smoothly so to me that doesn't say compression issue. I have a compression and a leak down tester so I'll likely check anyway to be sure.

 

I have 5k and 5 months remaining on the drivetrain warranty so I better figure it out soon.

 

obviously, im guessing with the limited amount of info i havfe

but trying to point you in the right direction

 

Okay. Whew. You scared me man. I'll test the coils first then go from there.

 

Can't seem to find the ignition coil resistance values in the service manual. Anyone have those numbers handy (2011 Acura TL SH-AWD)

 

It's not in my 2012 manual either.

 

check and see if the transmission software was updated as the old software damaged torque converters.

 

Wouldn't a damaged torque converter exhibit slippage and/or chattering and/or vibration though? I don't have any of those symptoms.

 

^you're giving us VERY limited info....
so, all we're doing is Suggesting what it could be...and maybe its not the right suggestion...but it should get you thinking on how to resolve...

 

Yeah, I know. That's because I haven't had a chance to dive into it yet. I've only had the vehicle for a couple months and it's been sitting for over half of that time because of the airbag recall. I'll do some basic checks (coil resistance, compression, leak-down, etc) and post back at a later date. Unfortunately, it looks like I need and HDS tool to disable the injectors in order to do a compression test. However, a leakdown would be more comprehensive anyhow.

 

a failing catalytic converter can also cause hesitation

 

and agreed, leak down will be more conclusive

 

Didn't even think of that. How would one diagnose a failing converter other than replacing it with a new one? Measure O2 sensor voltage differential between the exhaust manifold and downstream of the converter?

 

Still no luck finding specs on the coil pack resistance. Very puzzling. I measured between 1.8k and 1.9k on the primary coils and 3.1M to 3.3M on the secondary coils for all of them.

 

My best guess is they don't provide them because it's not a tell-all. In other words, the resistance can be within spec, but that doesn't mean the coil is functional. I'll have to take some measurements with an o-scope to gauge their health.

 

I have a 2013 RDX FWD it shows intermittent misfires on 4-5 and 6, i have replaced all coils with no fix yet. Wondering if it could be fuel injector relay module or the ECU. Any thoughts anyone?